What does serving size mean? Is it how much you’re supposed to eat? Is it a dietary guideline?
You might be surprised to know that it’s neither!
The serving size listed on a food label is actually a standardization created to allow you to compare different foods.
If you look at the bottom of a Nutrition Facts panel, you’ll see that it’s based on a 2000 calorie diet – the standardization that everything else on the label is based on. So a serving size of 2/3 cup means: if you eat 2/3 cup of this food, you will consume X proportion of 2000 calories.
So surely there must be a good reason why 2000 calories is the standardization…right? Right?
Oof, I wish. The FDA arrived at 2000 calories based on self-reported surveys from men, women, and children of how much they ate per day (self-reported information is notoriously unreliable). Well, actually, based on those surveys, they chose to go with 2350 calories. But, when critics worried that setting it at 2350 would encourage people to overeat, they decreased it to 2000 calories. (See FDA calorie recommendations here).
However, while the methodology behind Nutrition Facts labels leaves a lot to be desired, the information on the label is not completely useless. It still can give you a rough idea of that food’s nutritional content. And it does allow you to compare different foods to each other. It can also serve as a starting point for finding a reasonable serving size for you.
However, you should not be eating what the serving size states just because that’s what’s on the label. And you definitely shouldn’t feel guilty if you eat more than the serving size.